Force-multiplying mechanisms

ABSTRACT

We disclose, in force-multiplying apparatus adapted for elevating heavy loads and the like, the combination comprising mechanical advantage means disposed to translate a relatively smaller input force to a relatively larger elevating force, and means for continuously applying a fluid pressure to the elevating component of said mechanical advantage means.

United States Patent 8 [151 3,680,400

Lemper et al. 1 Aug. 1, 1972 154] FORCE-MULTIPLYING MECHANISMS 2,937,984 5/1960 Chapellier ..254/93 A [72] Inventors: Herbert Lemper; William J. Snee 3,031,397 4/1962 Fortescue et a1 ..254/93 A Jr both of Pittsbur h Pa 2,278,786 4/1942 Johnston ..83/320 g 2,287,833 6/1942 Ridgway ..83/318 [73] Assignee: Mesta Machine Company, Pitt- 2,808,104 10/1957 Peterson ..83/320 sburgh, Pa. 3,040,609 6/1962 Bowman ..83/318 [22] Filed: May 14 1969 3,353,352 11/1967 Gardner ..60/51 [21] Appl. No.: 870,062 Primary Examiner-William F. ODea Assistant ExaminerWesley S. Ratliff, Jr. Related Appllcatwn Data Att0rneyBuel1, Blenko and Ziesenheim [62] Division of Ser. No. 544,198, April 21, 1966,

Pat. No. 3,453,914. [571 ABSTRACT We disclose, in force-multiplying apparatus adapted Cl. -l 254/93 A, 83/ 2 for elevating heavy loads and the like, the combina- /51 tion comprising mechanical advantage means disposed [51] Int. Cl ..F16h 27/02 to translate a relatively smaller input force to a rela- [58] Field of Search....83/320, 318; 60/51; 74/8915; tively larger elevating force, and means for continu- 254/93 A ously applying a fluid pressure to the elevating component of said mechanical advantage means.

[56] References Cned 11 Claims, 2 Drawing Figures UNITED STATES PATENTS 2,875,980 3/1959 Grace ..254/93 A 154 x x e ms :44 :53 128* 5 [48 M3 PATENTED M18 1 I972 SHEET 2 OF 2 Om mm/ vv vm mm Om INVENTORS,

HERBERT LEMPER WILLIAM H. SNEE,JR.

their ATTORNEY) FORCE-MULTIPLYING MECHANISMS The present application is a division of our copending application entitled Force-Multiplying Mechanisms, filed Apr. 21, 1966, Ser. No. 544,198, now US. Pat. No. 3,453,914.

The present invention relates to force-multiplying means which are adapted for the application of relatively very large forces over relatively short distances and finds application in the construction'of a wide range of power tools, for example, various types and sizes of presses, shears, cutters and the like. The invention is particularly useful in such applications where space is at a premium.

Although the present invention is described in the context of movable or flying shears used in a continuous casting machine, it will be apparent from a detailed perusal hereof that our force-multiplying mechanism is amenable to other applications. 7

In an exemplary application of the invention, the force-transmitting means are associated with relatively large capacity force-transmitting members, such as shears used in the steel industry for various applications. In certain modifications of this form of the invention, our novel force-transmitting means are described in connection with a novel arrangement of a large capacity bloom shear which is particularly adapted for use in a continuous casting machine. Although not limited thereto, our invention is particularly useful with a vertical casting machine to enable the aforementioned shear to follow the vertically moving strands during the interval in which the cut is being made by the shear. After completing the cut the shear must'be returned to its starting position by our novel force-multiplying mechanism.

Under these conditions it is necessary to minimize ble power must be expended in the operation of conventional shearing mechanism for thus moving the shears, and, of course, such power is multiplied by the number of strands of such apparatus. Accordingly, for the several shears required, a number of relatively large and expensive jacks or other lifting means and drives therefor had to be incorporated into an already overcrowded production area.

The time allowed for shearing the blooms, or strands, of course, is determined by the casting speed of the continuous casting machine and by the space which can be allotted for lowering and raising the shears during and after making the cut. In the aforementioned specific example, the casting speed of the continuously moving strands is' about 16 feet per minute while the allowable vertical reciprocative distance of the individual shears is about 4 feet. Thus, the cut must be made within about 15 seconds. Obviously, however, if a given one of the shears fails to complete a cut, the entire strand is lost in production, which is only an initial por- 'tion of the total loss of production during the time again by the relatively large number of convential liftthe physical size of the shear and its supporting or for each casting machine and are associated respectively with the individual strands or blooms issuing from the molds, must be able to apply sufficient force to the blades of the shears in order to make each cut in a matter of seconds. For a typical bloom mill, the continuous casting machine, when fabricating 12-56 by 12- ;z blooms for example, must be able to sever or cut the strands into the desired lengths, with about 15 seconds being allowed for each cut. During this interval the novel shear supporting mechanism of our invention is adapted to synchronize the speed of each shear with that of the strands being cut thereby so that the cut can be completed within the specified time without interfering with the operation of the casting machine or of the shear itself.

While the cut is being made, suitable means must be provided to lower or otherwise move the shears in the direction of strand movement and at the speed of the associated strand while the cut is being made and then to return the shears to their starting positions. Because of the extremely heavy weight of the shears, consideraing jacks or other transmitting linkages for the shears. Besides the high procurement, construction and maintenance costs, the physical sizes of the large elevator or lifting mechanisms for the shears occupy much valuable manufacturing floor area.

These difficulties are overcome by our disclosed force-multiplying means for conveniently elevating or otherwise moving a flying shear arrangement or other relatively heavy apparatus. Our present invention is particularly amenable for synchronizing the speed of the flying shear with that of the casting machine strands, in a specific application. Although obviously not limited thereto, our presently described force-multiplying mechanism is described in connection with that specific shear structure shown as in the accompanying drawings, but claimed and described more completely in our aforementioned co-pending application.

Thus, in a force-multiplying mechanism for moving one or both blades of the shears, an eccentric is provided for imparting relatively small increments of motion to one of the shear blades, and then during each the backstroke of the eccentric, spacing means are adjustably coupled to the one or to the other of the blades to provide incremental movement thereof toward the other blade until the cut is completed. The shear drive shaft is provided with an eccentric having only a minor fraction of the throw required in conventional shears to make the necessary cut, but is operated several times during the course of making the cut in order to afford the aforementioned incremental moving of the shear blade coupled to the adjustable spacing means until the shear blades are substantially closed or until the cut is completed. Thus, for purposes of comparison, it may be assumed that the novel eccentric arrangement of the invention is provided with a A inch throw and thus the torque required is 3 million pounds times 0.25 inch or only 750,000 inch-pounds. Therefore, assuming that the shear blade is operated incrementally throughout the entire stroke of inches, the eccentric can be rotated not at 4 rpm as in the conventional case, which requires 22 1% million inch-pounds, but at the rate of 30 revolutions for each cut or 120 rpm. This arrangement permits a high speed (1,200 rpm, for example) and much less expensive and complex electric motor drive to be utilized instead of the 250 rpm motor. Moreover, the speedreduction unit need be only a 10 to 1 ratio of considerably lighter construction rather than the 62.5 to 2 ratio of conventional constructed arrangements.

The force-transmitting mechanism associated with the elevating arrangement for the shears or other appropriate and usually massive machinery is provided with novel weight counter-balancing means associated therewith whereby the major proportion of the weight of the apparatus being elevated is counter-balanced at all times during use thereof. If one arrangement of the last-mentioned force-transmitting mechanism, when used with a continuous casting machine, hydraulic counter balancing means are employed to support for example 90 percent of the weight of each of the several shears used in the casting machine. Since the counterbalancing force is continuously applied, the operating components of the lifting mechanism for raising and lowering the shears can be of much lighter construction, and therefore, is less complicated, easier to maintain, and less subject to wear.

Most importantly the lifting mechanism is not subjected to reversals in direction of movement under the full weight of the shear or other load, butrather under only a small fraction thereof. As a result wearing of the components of the lifting device particularly the moving parts thereof is considerably reduced. The motive power supplied to the gearing or other force-transmitting means forming part of the lifting means of this feature of the invention is correspondingly reduced together with the physical sizes of the inter-connecting drive shafts and other related components.

Because of the much lesser torques required for a given application of the force-multiplying mechanism of the invention, the latter can be made correspondingly smaller in size and thus are equally adaptable for use in extremely large elevating means or in presses or the like. The principles of our invention can be used to advantage and with relative facility in either very large or relatively small lifting devices. The force-transmitting means of the invention makes possible the construction of elevating mechanisms, presses or the like having capacities which are not otherwise feasible, particularly where space limitations impose restrictions on the sizes of the individual components.

We accomplish these desirable ends by providing in force-multiplying apparatus adapted for elevating heavy loads and the like, the combination comprising mechanical advantage means disposed to translate a relatively smaller input force to a relatively larger elevating force, and means for continuously applying a fluid pressure to the elevating component of said mechanical advantage means.

We also desirably provide a similar force-multiplying mechanism wherein said mechanical advantage means includes a jack mechanism, the traversing screw of which is provided with a cavity extending longitudinally therethrough in the direction of traversing screw movement, said cavity being closed at the lifting end of said traversing screw and open at the other end, and means are provided for introducing a fluid pressure into said hollow so as to apply lifting force to said closed screw and for at least partially counter-balancing the weight of said load.

We also desirably provide a similar force-multiplying mechanism wherein said fluid introducing means includes a stationary plunger mounted on said mechanism and closely fitted within said cavity, said plunger being elongated in the path of said traversing screw travel to maintain engagement therewith and having a fluid pressure extending axially therethrough for introducing fluid into said cavity between the inserted end of said plunger and said closed screw end, and mean for coupling said passage to a source of pressurized fluid.

In the foregoing, various objects, features and advantages of the invention have been alluded to. These and other objects, features and advantages of the invention will be elaborated upon during the forthcoming description of certain presently preferred embodiments of the invention together with preferred methods of practicing the same.

In the accompanying drawings, we have shown certain presently preferred embodiments of the invention together with presently preferred methods of practicing the same, wherein:

FIG. 1 is a side elevational view, partially in section, of one form of shearing mechanism arranged in accordance with the invention and incorporating the aforementioned force-multiplying means for actuating the shear blade and for lowering and raising the shearing apparatus; and

FIG. 2 is a longitudinally sectioned view of the apparatus as shown in FIG. 1 and taken along reference line IIII thereof.

Referring now more particularly to FIGS. 1 and 2 of the drawings, the exemplary force-transmitting apparatus such as shears 10 shown therein includes a casing 12 which is formed inter alia from a pair of sidewall supports 14. The supports 14 are laterally spaced, as better shown in FIG. 2, and each is provided with longitudinally extending, aligned slots 16, and a slideway structure 18 formed along the upper and lower edges of the slot 16, as better shown in FIG. 1' of the drawings. In this example, the stationary shear blade structure or knife block 20 is positioned between the supports 14, as better shown in FIG. 2, adjacent the right-hand end portion of the slots 16.

A movable shear blade structure or knife block 22 likewise extends between the supports 14 and slidably engages the slideway means 18 of each support slot 16. The knife blocks 20 and 22 are each provided with shear blades 24 and 26 respectively, which are mounted thereon in the usual fashion.

In FIG. 1 of the drawings, the movable knife block 22 is shown in its withdrawn position to define an opening between the shear blades 24, 26 through which a bloom strand 28 or the like is spacedly inserted between cutting operations. A driver 30 likewise extendsbetween the lateral supports 14 and is supported upon the slideway 18 of the support slots 16 for movement longitudinally of the supports 14. Means presently to be described are coupled to the driver 30 for reciprocating the driver through a relatively short path of travel. Knife block or shear spacing and withdrawal means denoted generally by the reference character 32 are likewise mounted upon the lateral supports 14, in this example, and are utilized for converting the reciprocating movement of the driver 30 to a continuous stepwise movement of the movable knife block 22 in its cutting direction and then for quickly withdrawing the movable knife block 22 after the cutting operation is completed. The shear spacing and withdrawing means 32 likewise will be described in greater detail hereinafter.

One arrangement for reciprocating the driver 30 in accordance with the invention includes the provision of crank means such as pitman 34 positioned between the lateral supports 14 and pinned to a transverse drive shaft 35 extending through the driver 30. In this arrangement the drive shaft 35 desirably is rotatably mounted in the driver 30, for which purpose a sleevetype bearing 37 can be provided, in order to compensate for any slight misalignment of the driver 30 relative to the pitman 34 owing to manufacturing tolerances or the like.

The pitman 34 is reciprocated, together with the driver 30 which is coupled thereto, by means of an eccentric mounted on the main or input drive shaft 36 of the apparatus. The drive shaft 36 likewise extends transversely of the lateral supports 14 on which it is mounted through suitable antifrictional means such as the roller bearings 38. The main drive shaft 36 is rotated by means of a worm gear 39 which is pinned to the drive shaft 36 for rotation therewith. As better shown in FIG. 1 of the drawings the worm gear 39 and drive shaft 36 are rotated by means of a worm 40 mounted on the lateral supports 14. The worm gear 40 is rotatably mounted desirably on the lower edges of the lateral supports 14, as better shown in FIG. 2 of the drawings, upon suitable bearings 41, and is provided at one end with a stub shaft 42 to which a suitable drive (not shown) is coupled for rotating the worm 40.

In this arrangement of the invention, the pitman 34 is of dual construction for maximum strength and for symmetry of force transmission. The components of the pitman 34 are spaced by means of a web 44 and, in this example, straddle the worm gear 39 for rotatable mounting on the hub extensions 46 and 48 respectively of the worm gear 39. As better shown in FIG. 2, each hub portion 46 or 48 is eccentrically disposed relative to the centerline 50 of the main drive shaft 36, with the hubs 46, 48 being unidirectional in eccentricity. The pitman components are rotatably mounted on the eccentric hub portions 46 and 48 respectively by means of suitable antifrictional means 52, which can be similar if desired to the shaft bearings 38. Accordingly, as the main drive shaft 36 is rotated a reciprocation of relatively small stroke is imparted to the pitman 34 and thence to the driver 30. In this example of the invention, the driver 30 and the pitman 34 are reciprocated within a rectilinear dimension of about one-half inch, and accordingly, the eccentrics represented by the hub portions 46 and 48 have a throw of about one-fourth inch. It will be understood, of course, that the eccentries can be otherwise formed on the main drive shaft 36 but are provided as shown in FIG. 2 for maximum strength and conservation of space, which, as pointed out previously, is at a premium in this application of the invention.

It will also be readily understood that the aforementioned stroke and throw can be correspondingly varied from the dimensions given so that the driver 30 and the pitman 34 can be reciprocated within a smaller or larger distance as required by a particular application of the force-multiplying mechanism. The important feature of the invention is that each stroke of the driver 30 be a fraction of the total cutting distance through which the movable knife block 22 must be actuated to sever the bloom 28 or other workpiece inserted between the shears 20-22.

One arrangement for converting the reciprocatory movement of the driver 30 into incrementally continuous or stepwise cutting movement of the movable knife block 22 will now be described. In this arrangement the driver 30 is spacedly coupled to the movable knife block 22 by means of a jack screw or other appropriately sized screw 54 or the like. The threaded portion 56 of the screw 54 is threadedly engaged with the movable knife block 22 by means of a threaded nut 58 which surrounds at least a portion of a longitudinally extending aperture 60 of the knife block 22. At its outer end, the screw 54 is rotatably joined to the driver 30 by means of its headed portion 62, which is retained on the driver 30 by means of an apertured clamp plate 64 engaging the outer periphery of the headed portion 62.

An annular bearing 66 is recessed centrally into the adjacent face of the driver 30 and in this example the headed portion 62 is provided with a centering pin 68 which is engaged in the opening of the annular bearing 66 in order to align the screw 54 with the driver 30. Desirably, the bearing 66 and the adjacent surface of the headed portion 62 of the screw are provided with complementary spherical surfaces denoted generally by the reference character 70 to accommodate any slight axial misalignment of the screw 54 and the driver 30 which may occur during operation of the shear.

The threaded portion 56 of the screw 54 preferably is recessed within the movable knife block 22 to the extent at the withdrawn position of the shear that upon rotation of the screw 54 and its unthreading from the knife block 22 the latter is moved through the distance required to make the out while still maintaining adequate threaded engagement between the screw 54 and the knife block 22.

In the operation of the shear, the screw54 is maining and knife block withdrawing means 32, alluded to previously, are provided for rotating the screw 54.

Desirably, the screw 54 is rotated at such speed that the movable knife block 22 remains motionless during each withdrawal movement of the driver 30. Thus, the blade 26 of the knife block 22 is advanced stepwise through the material of the workpiece being cut, during the forward strokes of the driver 30.

In many applications of the invention, the workpiece is completely sheared or severed when the blade 26 of the movable knife block 22 has passed between twothirds and three-fourths of the thickness of the workpiece. Accordingly, a limit switch 74 can be positioned as shown in FIG. 1 at a location suitably spaced from the blade 24 of the fixed knife block 20, preferably on one of the lateral supports 14 so as to be out of the path of the. severed workpiece section, in order to reverse the aforesaid rotating means for the screw 54. During such reverse movement of the rotating means, as described hereinafter in greater detail, the screw 54 is continuously rotated in the counter-clockwise direction in this example, in order to withdraw rapidly the movable knife block 22 to its retracted position shown in FIGS. 1 and 2.

An exemplary arrangement of theinvention isillustrated in FIG. 1 for intermittently rotating the screw 54 for the purpose of increasingly spacing the movable knife block 22 from the driver 30 during the cutting operation and for continuously rotating the screw 54 in the opposite direction for rapid withdrawal of the movable knife block 22 following the cutting operation. Such rotational means, in this example, includes a spur gear76 rotatably mounted on a suitable bearing arrangement 78 which is in turn supported by a pair of generally parallel transversely extending supporting plates 80. In this arrangement the plates 80 extend between and are secured to the lateral supports 14. The spur gear 76 is movably keyed to the screw 54 for rotation therewith by means of one or more keying'members 82, with one such keying member being employed in this example. The keying members 82 are recessed into the surfaces of the screw 54 and are slidably engaged in respective grooves 84 extending transversely within the hub structure of the spur gear 76. With this arrangement the screw 54 can be reciprocated transversely of the spur gear 76 while still remaining keyed thereto for rotation therewith.

An idler gear 86 is mounted on a shaft supported in the extension 88 of gear housing 90, which is formed by the spur gear supports 80 and by a metal band 92 extending therearound. The idler gear 86 is in turn enmeshed with pinion 94, which in turn is secured for rotationon an output shaft 96 of drive motor 98 for the aforementioned gearing train. In this arrangement the drive motor 98 is mounted upon supporting plate 100 extending transversely between the lateral supports 14 and secured at its ends thereto.

In this arrangement of the invention, the pitch of the threaded portion 56 bears a spatial relationship to the stroke of the driver 30. For example, the pitch of the threaded portion 56 can be such that the screw 54 is rotated twice during each withdrawal movement of the driver.30 and pitman 34 as caused by rotation of the eccentrics 46-48. The motor 98, which will of course be rotated a larger number of times depending upon the specific gearingv relationship between the spur and pinion gears, can if desired be operated intermittently through a suitable switching arrangement (not shown) coupled to or otherwise energized by the eccentrics 46-48. On the other hand, when the movable knife block 22 has been advanced to the reversing switch 74, after the workpiece segment has been sheared, the motor 98, through other circuitry in parallel with the aforementioned circuitry and actuated by the reversing switch 74, can if desired be energized to rotate the screw 54 continually in the opposite direction until the movable knife block 22 is completely and rapidly withdrawn. At the latter position of the movable knife block 22, a second limit switch (not shown) desirably is positioned to again reverse the rotation of the motor 98.

Preferably, however, the driving means 98 is provided in the form of a low-speed electric motor which can be intermittently stalled without damage thereto. In-the latter arrangement, the motor 98 is continuously energized during forward movement of the movable knife block 22. Thus, when a cut is to be made, the motor 98 is energized and the screw 54 is rotated to rapidly advance the movable knife block 22 across the gap which normally exists between the cutter blade 26 and the workpiece 28 at the fully withdrawn position of the movable knife block 22. When the movable knife block 22 thus engages the workpiece 28, the motor 98, of course, stalls and the succeeding forward stroke of the driver 30 loads the screw 54 to prevent further rotation thereof in either direction and to maintain the spacing then existing between the movable knife block 22 and the driver 30. The driver 30 continues through the forward stroke to advance the movable knife block 22 through the first increment of its cutting movement. At the end of the forward stroke, the driver 30 reverses to unload the screw 54 whereupon the screw 54 is again rotated by the continuously energized motor 98 to take up the increased spacing between the driver 30 and the movable knife block 22 afforded by the reverse stroke of the former. The succeeding forward stroke of the driver 30 again loads the screw 54 against rotation and advances the movable knife block 22 a second increment of the cutting movement of the shear. Incremental movement of the movable knife block 22 is continued in this manner until the blade 26 thereof hasv been moved through between two-thirds and threefourths of the thickness of the workpiece, at this point shearing thereof is usually completed. At this point the limit switch 74 is engaged by the movable knife block 22 to rapidly retract the movable block as explained above. Increased speed of shear transit is, of course, impossible in conventional eccentric-actuated machines since the eccentric induces only a single forward stroke for each cut. Thus, the force multiplying mechanism incorporated in the shears aids in performing the cutting operation with much less applied torque in less time.

For use in vertical continuous casting machines, the

shearing apparatus of FIGS. 1 and 2 of the drawings desirably is used with an elevating table such as that denoted generally by reference character 112 and likewise shown in FIGS. 1 and 2 of the drawings.

Referring again to the latter figures the elevating table 112 includes a pair of uprights 114 which are generally laterally aligned with the lateral supports 14 of the shearing apparatus, and a bridging plate 1 l6. Appropriate bearing or wear strips 118 and 120 desirably are sandwiched respectively therebetween to facilitate sliding engagement of the lower edges of the lateral supports 14 with the upper edges of the elevating table 112. The shearing apparatus thus can be moved longitudinally of the elevating table 112 by conventional positioning apparatus denoted generally by reference character 122 and including lever 124 and link 126.

In this specific application of the invention, the elevating table 112 and with it the shearing apparatus desirably is lowered and raised each time a cut is made, by means of a pair of force-multiplying mechanisms 128 constructed in accordance with the invention. In this arrangement, the force mechanisms 128 are arranged generally in the form of screw jacks and are spaced so as to engage the end portions respectively of the elevating table 112. Therefore, as better shown in FIG. 1 of the drawings, each of the lifting means 128 are provided with a worm gear 130, and the worm gears 130 are driven simultaneously in this example by a pair of worms 132 respectively, which are spacedly mounted upon drive shaft 134 for rotation therewith. The drive shaft 134 is coupled to suitable conventional driving means such as electric motor 136.

Each worm gear 130 is rotatably mounted upon suitable anti-frictional means 138 which in turn are mounted in gear casing 140 forming pair of the lifting means housing 142, which in turn is mounted upon support 143. The worm gear 130 is provided with a central, tapped aperture or elevating screw 131 whereby the gear threadedly engages a hollow traversing or jack screw 144, and thus rotation of the worm gear 130 raises and lowers the jack screw 144 in the conventional manner, as the latter is secured against rotation to the underside of the elevating table 112. A sealed bellows 146 if desired, can be provided between the traversing screw and housing to protect the housing 142 and the parts therein against entry of dirt or other foreign matter. The reversible driving means 136 can be rotated in either direction to raise and lower the elevating table 112 as desired. Desirably, also the driving means 136 is of a variable speed variety, so that the elevating screws and the shear can be speed-matched with the casting machine strands.

However, in order to considerably reduce the load stresses which must be carried by the motor 136, the shaft 134 and the aforedescribed components of the screw jack, means are provided in accordance with the invention for continuously applying a biasing or counter-balancing force to the elevating table 112. Such counter balancing force in effect reduces to a large extent the weight of the elevating table 112 and the shear supported thereon which must be carried by the moving components of the lifting mechanism 128. Desirably, the weight of the elevating table 112 and the shearing apparatus 10 are not completely counterbalanced so that some load remains applied to the lifting mechanism to avoid backlashing gears and other tolerances. However, it is contemplated that in certain applications, it will be desirable to entirely counterbalance the weight of the aforemention table and the shears or other apparatus which may be carried by the lifting mechanisms 128. In still other applications, it

may be desirable to over counter-balance the load carried by the lifting mechanism 128 rather than to under counter-balance such loads. By thus'reducing the loads carried by the jack screws 144 the speed at which the shear is lowered in this application, can be more quickly accurately and reliably matched with the speed of the associated machine strand.

One form of such counter-balancing means of the invention includes the provision of a hollow or apertured supporting and stabilizing stud 148 for the jack screw 144, which stud is flanged at its lower end for securance to the housing 142 .of the lifting mechanism. At the retracted position of the jack screw 144, the stud 148 desirably extends substantially along the length of the jack screw 144 and through its internal cavity 150.

The stud 148 is supported by the housing 142 and support 143 and the integrity of the sealed housing 142 is preserved by suitable sealing and supporting means such as annular plate 149 disposed at the junction of the housing 142 and the stud or stationary piston 148. More importantly, however, the stud 148, and sealwelded, for example, thereto is sealed to the inner wall surfaces of the hollow traversing screw 144 by suitable means such as hydraulic packing 151 which is retained in the position shown by an annulus 152 which is bolted or otherwise secured to the lower end of the traversing screw 144. Additional sealing capability can be provided if desired by a labyrinthine seal 153, extending along the length of the stud 148. Alternatively the packing 151 can be so extended. The threaded engagement of the worm gear and the traversing screw 144 is such that at the lowermost position of the traversing screw 144, as viewed in FIG. 1 of the drawings, the upper end of the jack screw 144 does not engage the upper end of the stud 148 in order to leave a pressure distributing gap therebetween in order to provide a desired mechanical advantage. The plunger or stud 148 is of such length that an interfitting engagement thereof with the jack screw 144 is maintained throughout its path of longitudinal movement.

With the arrangement just described, the stud 148 serves as a plunger, which, however, is maintained at a stationary position by its securance to the housing 142, while the hollow jack screw 144 serves as a movable cylinder. By the same token the housing 142 is also stationary, which facilitates coupling of the drive mechanism 130-136 thereto. Accordingly, a passage 158 extends longitudinally therethrough and when the conduit 156 is coupled to a suitable source (not shown) of hydraulic fluid or the like, pressure is transmitted to the gap 154 in order to apply a continuous lifting force to the adjacent surface of the topportion of the jack screw 144. Desirably, the conduits 156 of both lifting mechanisms 128 are coupled to a suitable accumulator 157 of conventional construction so that the forces thus transmitted to the jack screws 144 are notchanged as the latter are extended or retracted to raise and lower the elevating table 112. The accumulator 157 can be coupled to a suitable source (not shown) of pressurized fluid through conduit 159. The pertinent diameters of the stud 148 and the jack screw 144 can of course be varied depending upon the amount of counter-balancing lifting force which is desired to be applied to the top portion of the jack screws 144 and hence to the elevating table 112 and other apparatus carried by the lifting mechanism 128.

In an exemplary application of thisfeature of the invention, a summation of the counter-balancing forces thus applied by the lifting mechanism can equal 90 percent of the total weight of the shearing apparatus and the elevating table 112, with the result thatv the power and attendant size of the drive motor 136, can be reduced to about 10 percent. Similarly, the corresponding sizes of the drive shaft and the gearing train l30-132 can be reduced. Such reductions obviously will result in substantially reduced procurement and maintenance costs of the lifting mechanism. Most importantly, a more accurate operation of the lifting mechanism results.

From the foregoing it will be apparent thatnovel and efficient forms of force-multiplying mechanisms have been disclosed herein. Although the mechanisms have been described in connection with certain exemplary apparatus, and formed in certain cases as parts of such apparatus, it will be understood that the mechanisms are, however, of general utility. As indicated by the several applications of the invention described herein, the force-multiplying mechanisms can be provided in a wide range of sizes and configurations within the teachings of the invention, in order to adapt the mechanism to a variety of force-transmitting apparatus and to wide ranges of sizes thereof. It is also contemplated that the force-mechanism invention can be operated to separate the force-transmitting members against suitably applied load means. Moreover, it will be understood that certain features of the invention can be utilized without a corresponding use of the features. Accordingly, we have shown and described certain presently preferred embodiments of the invention and have illustrated presently preferred methods of practicing the same,- it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

We claim:

1. In force-multiplying apparatus adapted for elevating heavy loads and the like, the combination comprising mechanical advantage means disposed to translate a relatively smaller input force to a relatively larger elevating force, said mechanical advantage means including a relatively stationary support structure, and internally threaded elevating screw rotatably mounted on said support structure, an externally threaded jack screw threadedly engaged with said elevating screw and thereby disposed for longitudinal movement relative to said support structure and said elevation screw, elongated chamber means extending through said jack screw and delimited at one end by a closed load bearing end portion of said jack screw, a source of pressurized fluid coupled to said chamber means for continuously applying a fluid pressure to said chamber means and to said load bearing end portion, and means for rotating said elevating screw for longitudinal movement of said jack screw relative to said support, said stud member being inserted into said chamber means throughout said jack screw movement.

2. The combination according to claim 1 including a stud member shaped for closely fitting sliding insertion into said jack screw chamber means, said stud member having fluid passage means extending therethrough' into communication with said chamber means, said source being c nnected to said passage neans.

3. The com matron according to c a said apparatus includes an elongated table, and a pair of said mechanical advantage means are mounted to support respectively the end portions of said table, the chamber means of each of said mechanical advantage means being coupled to a common source of pressurized fluid.

4. The combination according to claim 3 wherein said source includes an accumulator coupled to both of said chamber means.

5. The combination according to claimv 1 wherein said elevating screw is mounted on a worm gear rotatably mounted on said support, and means including a worm rotatably mounted on said support are provided for rotating said worm gear;

6. The combination according to claim 5 wherein two such mechanical advantage means are provided for engagement with a single. load, and the rotating mean of each of said mechanical advantage means are coupled to a common drive mechanism.

7. The combination according to claim 1 wherein said support includes a housing substantially enclosing said jack screw and said elevating screw, and said rotating means are at least partially enclosed within said housing.

8. The combination according to claim 7 wherein said elevating screw is mounted on a worm gear for rotation therewith, said worm gear and worm therefor being rotatably mounted and substantially enclosed within a gear casing forming part of said housing.

9. The combination according to claim 1 wherein expansible sealing means are sealed to said closed end portion and to said support .for sealing the junction between said jack screw and said support.

10. The combination according to claim 8 wherein said closed end portion protrudes through said gear casing, and sealing means are secured to said closed end portion and to said casing for sealing the passage of said jack screw therethrough.

11. The combination according to claim 2 including means extending along the length of said stud means for sealing said jack screw thereto.

1m 1 wherein v 

1. In force-multiplying apparatus adapted for elevating heavy loads and the like, the combination comprising mechanical advantage means disposed to translate a relatively smaller input force to a relatively larger elevating force, said mechanical advantage means including a relatively stationary support structure, and internally threaded elevating screw rotatably mounted on said support structure, an externally threaded jack screw threadedly engaged with said elevating screw and thereby disposed for longitudinal movement relative to said support structure and said elevation screw, elongated chamber means extending through said jack screw and delimited at one end by a closed load bearing end portion of said jack screw, a source of pressurized fluid coupled to said chamber means for continuously applying a fluid pressure to said chamber means and to said load bearing end portion, and means for rotating said elevating screw for longitudinal movement of said jack screw relative to said support, said stud member being inserted into said chamber means throughout said jack screw movement.
 2. The combination according to claim 1 including a stud member shaped for closely fitting sliding insertion into said jack screw chamber means, said stud member having fluid passage means extending therethrough into communication with said chamber means, said source being connected to said passage means.
 3. The combination according to claim 1 wherein said apparatus includes an elongated table, and a pair of said mechanical advantage means are mounted to support respectively the end portions of said table, the chamber means of each of said mechanical advantage means being coupled to a common source of pressurized fluid.
 4. The combination according to claim 3 wherein said source includes an accumulator coupled to both of said chamber means.
 5. The combination according to claim 1 wherein said elevating screw is mounted on a worm gear rotatably mounted on said support, and means including a worm rotatably mounted on said support are provided for rotating said worm gear;
 6. The combination according to claim 5 wherein two such mechanical advantage means are provided for engagement with a single load, and the rotating mean of each of said mechanical advantage means are coupled to a common drive mechanism.
 7. The combination according to claim 1 wherein said support includes a housing substantially enclosing said jack screw and said elevating screw, and said rotating means are at least partially enclosed within said housing.
 8. The combination according to claim 7 wherein said elevating screw is mounted on a worm gear for rotation therewith, said worm gear and worm therefor being rotatably mounted and substantially enclosed within a gear casing forming part of said housing.
 9. The combination according to claim 1 wherein expansible sealing meAns are sealed to said closed end portion and to said support for sealing the junction between said jack screw and said support.
 10. The combination according to claim 8 wherein said closed end portion protrudes through said gear casing, and sealing means are secured to said closed end portion and to said casing for sealing the passage of said jack screw therethrough.
 11. The combination according to claim 2 including means extending along the length of said stud means for sealing said jack screw thereto. 